1. Field of the Invention
The present invention relates to image pickup devices for converting visual information to electrical signals and further reproducing the same as images, and portable telephones provided with such image pickup devices. More particularly, the present invention relates to an image pickup device and a portable telephone both downsized.
2. Description of the Background Art
FIG. 18 shows a schematic configuration of a conventional image pickup device. Referring to FIG. 18, an image pickup element 102 is mounted on the surface of a circuit board 101 by die bonding. An input/output terminal 117 of the image pickup element and a land portion 119 being a terminal of an interconnection pattern on the circuit board are connected by a wire 118 by wire bonding. In this image pickup device, optical information from an imaging lens, not shown, passes through a transparent plate 103 and is received at a light receiving plate 102a provided in image pickup element 102, and converted to an electrical signal. This electrical signal is sent from input/output terminal 117, through wire 118 to land portion 119, and to an interface portion (not shown). The transparent plate 103 is provided to seal light receiving plate 102a to prevent airborne dust from adhering thereto. Such a conventional image pickup device is too large in two dimensions and too thick to be mounted on a portable terminal device or the like.
An image pickup device reduced in planar dimension and thickness to improve light receiving efficiency is proposed (in Japanese Patent Laying-Open No. 9-199701), which has an image pickup element mounted on a mounting board with an opening and solely a light receiving area (an optical detection area) hermetically sealed. In this image pickup device, as shown in FIGS. 19A and 19B, the mounting board 101 is provided with an opening 101a that is formed so as not to interfere an optical path to light receiving plate 102a, and the image pickup element 102 is bonded face down. A terminal 119 of an interconnection pattern 101c of mounting board 101 and a bump 117 formed on a bonding pad of the image pickup element are aligned and bonded with each other. In this image pickup device, light receiving plate 102a is sealed by a transparent plate 103 and a sealing resin 121. In addition, the opening 101a on the mounting board is made sufficiently large with respect to the light receiving plate of the image pickup element, taking processing accuracy into consideration, so as not to interfere the reception of the light. Compared to the configuration as describe above, this image pickup device provides for a compact structure with reduced thickness and planar dimension.
The connection applying wire bonding as described above, however, increases the circuit board area in all directions. Moreover, the interconnection pattern in the image pickup device disclosed in Japanese Patent Laying-Open No. 9-199701 is placed to extend perpendicular to the edge of the opening, which hinders downsizing in the width direction. More specifically, as shown in FIG. 19A, the interconnection 101c of the circuit board is placed perpendicular to the edge of the opening 101a, and extends from the end portion 117 towards the outer shape of the image pickup element. Thus, the outer shape of the circuit board has a planar dimension greater than that of the image pickup element, thereby suppressing downsizing of the image pickup device.
Another image pickup device is disclosed (in Japanese Patent Laying-Open No. 5-260393), which has interconnections routed along the edges of the opening of the circuit board for the purposes of decreasing the planar dimension. In this device, however, the interconnection pattern is routed along the entire periphery of the opening. Thus, the effect to reduce the planar dimension was insufficient. To meet the stringent demands for downsized portable terminals of these days, a further decrease in planar dimension is required.
The configuration to mount an element on a circuit board face down, as described above, is well known in packaging of semiconductor elements, regardless of the type of the circuit board. As a circuit board for mounting the semiconductor elements therein, PCB (Print Circuit Board) of glass epoxy type, and FPC (Flexible Print Circuit) of a film shape, for example, are well known. However, an image pickup device that employs a film circuit board having an opening to let light pass therethrough as a circuit board for mounting an image pickup element face down thereon has not been known.
An object of the present invention is to provide an image pickup device and a portable telephone that are decreased in planar dimension and thickness.
The image pickup device according to a first aspect of the present invention includes: a circuit board provided with an opening portion and having an interconnection pattern formed of a plurality of interconnections and an interface region disposed therein; and an image pickup element placed on the circuit board and having a light receiving portion for receiving light from an imaging lens through the opening portion. The interconnection pattern is placed in an outer frame portion on a lateral side of the opening portion, together with a plurality of land portions being terminals of the respective interconnections, and extends to the interface region. At least one of the plurality of interconnections is placed between the land portions and the opening portion.
With the configuration as described above, it becomes possible to place the interconnection pattern in the outer frame portion surrounding the opening portion, not perpendicular to, but along the edge of the opening portion. Accordingly, the width of the outer frame portion of the opening portion can be reduced. Further, by disposing the interconnection pattern and the land portions (terminals of the interconnection pattern) that would take a relatively large space collectively in the outer frame portion on the same lateral side, the interconnection pattern can be placed compactly, without a need to route the same around the opening portion. The interconnection pattern may be placed exclusively between the land portions and the opening portion. Alternatively, a part of the interconnection pattern may be placed on the outer side of the land portions.
Herein, the xe2x80x9clateral sidexe2x80x9d of the opening portion refers to lateral or side portions thereof, when the circuit board is seen from its front surface side in an elevation view wherein the circuit board is arranged longer than is wide with an interface region being provided on an upper side or a lower side of the opening portion. The lateral side may include either or both of the left and right side portions. With the configuration as described above, it is possible to leave the outer frame portion on either upper or lower side of the opening portion, without placing the interconnection pattern therein. For example, in the configuration where the outer frame portion having such an empty space is to be provided on the upper side of the opening portion, a region for the interface portion is provided on the lower side of the opening portion. If the outer frame portion with an empty space is to be provided on the lower side of the opening portion, the interface region is provided on the upper side thereof. Thus, it becomes possible to minimize the frame width of the outer frame portion on either the upper or the lower side of the opening portion where the interconnection pattern is not being placed, and the interconnection pattern can be placed compactly. As a result, the region of the circuit board in which the image pickup element is to be mounted can be made small, thus enabling downsizing of the image pickup device. Throughout the specification, the xe2x80x9cback sidexe2x80x9d refers to the side of the circuit board on which the image pickup device is being mounted, and the xe2x80x9cfront sidexe2x80x9d refers to the side of the circuit board on which the transparent plate is being mounted. The xe2x80x9cfront surfacexe2x80x9d of each element refers to a surface of the element on the same side as the front side, and the xe2x80x9cback surfacexe2x80x9d of each element refers to its surface on the same side as the back side.
In the image pickup device according to the first aspect, all of the plurality of interconnections may be placed between the land portions and the opening portion. The interconnection pattern is placed in the outer frame portion within a region overlapping the image pickup element when seen in two dimensions.
With such a configuration, the mounting region of the image pickup element in the circuit board is utilized effectively by placing the interconnection pattern in the outer frame portion to overlap the image pickup element when seen in two dimensions. Thus, compared to the case where the interconnection pattern is placed in a region not overlapping the image pickup element, the size of the image pickup device can be reduced. As the image pickup element, a solid-state image pickup element CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) transistor or the like is employed. Accordingly, it becomes possible to downsize the image pickup element mounting region in the image pickup device to a maximum possible level of downsizing of the image pickup element, and to place the interconnection pattern in this image pickup element mounting region without expanding the region.
In the image pickup device according to the first aspect, each interconnection may include a first portion extending from the land portion towards the opening portion in a direction intersecting an edge of the lateral side of the opening portion, and a second portion extending continuously from an end of the first portion towards the interface region along the edge of the lateral side of the opening portion.
With such a configuration, it becomes possible to arrange the land portions each having a relatively large area in a line along the longitudinal direction of the outer frame portion, and to place the interconnections extending from the respective land portions along the edge of the opening portion at different distances from the opening portion successively. Accordingly, the interconnection pattern including the land portions can be placed in the outer frame portion in a very compact manner, so that the width of the outer frame portion can be reduced.
The image pickup device of the first aspect may further be provided with an adhesive agent between the circuit board and the image pickup element for adhesion thereof. The adhesive agent ensures conduction between the land portion on the circuit board and a corresponding bump on the input/output terminal of the image pickup element and isolation between the other portions.
When mounting the image pickup element on the circuit board, the land portion being a terminal of the interconnection pattern on the circuit board and a corresponding bump provided on the input/output terminal of the image pickup element are electrically connected to each other. Conventionally, an insulating layer having an opening corresponding to the land portions and bumps has normally been deposited on the mounting side of the circuit board, so as to prevent conduction between a bump and an interconnection that should not be connected to that bump or to prevent interconnections from being short-circuited with each other. The opening and an outer shape of the insulating layer are processed by blanking, and this blanking process and placement of the insulating layer are limited in accuracy to some extent. Therefore, in order to ensure desired connections between the bumps and the land portions even if variations would occur in the blanking and placing processes, the interconnection pattern including the land portions could not be downsized to an optimum level. More specifically, a minimum distance between the land portion in the interconnection pattern and the portion of the interconnection extending along the edge of the opening portion had to be made greater than a prescribed value. According to the present invention, however, the insulating layer is eliminated in the image pickup element mounting region, and the adhesive agent is employed instead. Accordingly, it is possible to reduce the minimum distance between the land portion and the portion of the interconnection extending along the edge of the opening, without the limitations as described above. As a result, the width of the outer frame portion surrounding the opening portion can further be narrowed, and thus, the image pickup device can further be downsized.
In the image pickup device of the first aspect, the adhesive agent may be an anisotropic conductive film (ACF) with conductive fillers distributed within a resin as an insulating binder. Thus, in a portion of the anisotropic conductive film where the resin is left aside as the land portion and the bump are close to each other, one or a plurality of the conductive fillers existing between the land portion and the bump can achieve conduction therebetween. In the other portions, the conductive fillers are distributed within the resin to maintain insulation.
By the use of the ACF above, it becomes unnecessary to dispose an insulating layer with an opening in the image pickup element mounting region. The ACF serves to reliably connect the land portion and the corresponding bump and to inhibit connection between the other portions.
In the image pickup device of the first aspect, minimum distances between the neighboring interconnections, between the neighboring land portions, and between the neighboring interconnection and land portion in the circuit board are each preferably at least 0.020 mm. A diameter of the granular conductive filler is preferably less than 0.010 mm.
With such a configuration, as long as the granular conductive fillers are separated from one another, it is possible to prevent short circuit between the portions that should not be connected to each other. By using such conductive fillers, conduction between the bumps and land portions as well as isolation between the other portions can be ensured without provision of the insulating layer in the mounting region. As a result, the minimum distance between the land portion and the interconnection can be reduced, and the outer frame portion where the interconnection pattern is being disposed can be narrowed. This enables further downsizing in planar dimension.
In the image pickup device of the first aspect, the circuit board may be a flexible, film circuit board.
By using the film circuit board to implement the circuit board described above, it becomes possible to further reduce planar dimension and thickness. When the film circuit board having the image pickup element and others bonded thereto is mounted on a product, it is slightly flexed or undulated to afford a certain margin or is loosely folded. Thus, the degree of freedom in placement of a connector portion of the product, e.g., a portable telephone, can be increased, and a space of the product being occupied by the image pickup device mounted thereon can be considerably decreased. The circuit board itself can also be reduced in weight.
The image pickup device according to a second aspect of the present invention includes an image pickup element that is mounted on a circuit board having an interconnection pattern formed of a plurality of interconnections disposed therein. The circuit board is provided with an opening portion, and includes a first region having an outside size that is approximately equal to or smaller than an outside size of the image pickup element and a second region having an interface region therein. The image pickup element is fixed in the first region such that a light receiving plane for receiving light faces with the opening portion. The interconnection pattern is formed on the first region in an outer frame portion on a lateral side of the opening portion and extends to the second region to electrically connect the image pickup element to the interface region in the second region.
With such a configuration, the outer frame portion of the opening portion can be effectively utilized by placing therein the interconnection pattern through which signals from the image pickup element are transmitted. In addition, the area of the interconnection pattern is restricted within the outside size of the image pickup element, and accordingly, the area of the outer frame portion is restricted to a small size.
In the image pickup device according to the second aspect, the circuit board includes a plurality of land portions being terminals of the respective interconnections that are arranged along a lateral edge of the opening portion. The interconnection pattern is formed in the outer frame portion of the lateral side of the opening portion, in a region between the land portions and the opening portion, and extends in a direction along which the plurality of land portions are arranged.
With the configuration as described above, by disposing the interconnection pattern and the land portions (terminals of the interconnection pattern) that would take a relatively large space collectively in the outer frame portion on the same lateral side, the interconnection pattern can be placed compactly, without a need to route the same around the opening portion. In addition, it is possible to leave the outer frame portion on either upper or lower side of the opening portion, without placing the interconnection pattern therein. For example, in the configuration where the outer frame portion having such an empty space is to be provided on the upper side of the opening portion, a region for interface portion is provided on the lower side of the opening portion. If the outer frame portion with an empty space is to be provided on the lower side of the opening portion, the interface region is provided on the upper side thereof. Thus, it becomes possible to minimize the frame width of the outer frame portion on either the upper or the lower side of the opening portion where the interconnection pattern is not being placed, and the interconnection pattern can be placed compactly. As a result, the region of the circuit board in which the image pickup element is to be mounted can be made small, thus enabling downsizing of the image pickup device.
The image pickup device according to a third aspect of the present invention includes: a flexible, film circuit board provided with an opening portion and having an interconnection pattern disposed on its back surface side; and an image pickup element mounted face down on the back surface of the film circuit board and having a light receiving portion for receiving light from an imaging lens through the opening portion.
With such a configuration, the image pickup device can further be reduced in thickness. The film circuit board with the image pickup element and others bonded thereto is slightly flexed or undulated to afford a margin or loosely folded when it is mounted on a product. Therefore, the degree of freedom in placing a connector portion of a portable telephone or the like is increased, and a space of the product being occupied by the image pickup device mounted thereon is considerably decreased. The circuit board is also reduced in weight.
In the image pickup device according to the third aspect, the film circuit board preferably has a thickness in a range between 0.020 mm and 0.050 mm.
By setting the thickness of the film circuit board within the range above, it is possible to quantitatively promote the reduction in thickness of the image pickup device.
In the image pickup device according to the third aspect, the opening portion of the film circuit board is preferably sealed by a transparent plate.
Provision of such a transparent plate adds rigidity to the film circuit board, which prevents it from undesirably curving, thereby allowing it to maintain a flat plate shape. Accordingly, easy handling of the film circuit board upon manufacturing is guaranteed.
In the image pickup device of the third aspect, a thickness T (TOTAL) from the back surface of the image pickup element to the front surface of the transparent plate is preferably not greater than 1.20 mm.
With such a total thickness T (TOTAL), it is possible to control and further promote the reduction in thickness.
In the image pickup device of the third aspect, the transparent plate is attached by adhesive means to either one of the film circuit board and the image pickup element. The adhesive means may include means for maintaining at least a prescribed distance between the transparent plate and the image pickup element.
With such a configuration, even if a thin film circuit board is used as the circuit board, it is possible to keep at least a prescribed distance from the transparent plate through the opening portion to the light receiving portion by simple means, thereby allowing formation of a good image.
In the image pickup device of the third aspect, spacer materials are preferably included in the adhesive agent for attachment of the transparent plate to the film circuit board.
By uniformly placing the spacer materials, it is possible to ensure at least a prescribed value of the thickness T (CLEARANCE) from the front surface of image pickup element to the back surface of transparent plate with a high degree of accuracy. This also has an effect to restrict deviation from parallelism of a relation between the front surface of image pickup element and the back surface of transparent plate within, e.g., 0.2 degrees.
In the image pickup device of the third aspect, the film circuit board may further be provided with a second opening portion, through which a thixotropic adhesive agent is disposed to attach the transparent plate to the image pickup element.
The thixotropic adhesive agent is an adhesive agent of high viscosity that is unlikely to deform or decay until it is cured or hardened. Provision of the thixotropic adhesive agent facilitates securement of the thickness T (CLEARANCE) of at least a prescribe value from the front surface of image pickup element to the back surface of transparent plate.
The image pickup device of the first aspect may be mounted on a portable telephone such that light from the outside of the casing of the portable telephone passes through the imaging lens and is received at the light receiving portion.
By mounting the image pickup device described above on the portable telephone, it becomes possible to downsize and lessen the weight of the portable telephone that is capable of transmitting an image of a good quality level for display.
The image pickup device of the first aspect mounted on the portable telephone may further be provided with at least one of a rubber connector and a peripheral circuit element. The circuit board is a flexible, film circuit board, and the film circuit board is folded such that a surface of at least one of the rubber connector and the peripheral circuit element contacts a back surface of the image pickup element, directly or indirectly with the film circuit board interposed therebetween.
With the use of the rubber connector above, provision of a molding connector or the like becomes unnecessary, so that a manufacturing cost can be reduced. Since the film circuit board is folded in two before being mounted on a product, a space of the product being occupied by the image pickup device is considerably decreased. The elasticity of the rubber connector provides a shock-absorbing effect against shock loading. The degree of freedom in designing the film circuit board can also be increased. Further, in the image pickup device requiring provision of the peripheral circuit element, the image pickup device and the peripheral circuit element can be stacked one on the other, so that a mounting area of the image pickup device on a product can be reduced, thereby enabling space saving.